Steam generators



N. P. RUSANOWSKY ETAL.

July 25, 967

STEAM GENERATORS 4 sheets-sheen 2 Filed Jan. 29, 1965 July 25, 1967 N. P. RUSANOWSKY ETAL. 3,332,402

STEAM GENERATORS Th. q

4 Sheets-Sheet 5 Filed Jan. 29, 1965 July 25, 1967 N. P. RusANowsKY ETAL 3,332,402

STEAM GENERATORS Filed Jan. 29, 1965 4 Sheets-Sheet 4 'TELCVEL United States Patent STEAM GENERATORS Nicholas P. Rusanowsky, Akron, and Robert W. Curtis, Alliance, Ohio, assignors to The Babcock & Wilcox gompany, New York, NSY., a corporation of New ersey Filed Ilan. 29, 1965, Ser. No. 429,007 S Claims. (Cl. 122-235) This invention relates generally to steam generators and more particularly to improvements in the combustion chamber of a water tube boiler of the shop-assembled, package type.

Shop-assembled oil and/or gas red steam generators are in great demand because of their lower cost and shorter delivery time as compared with the field assembled units of comparable capacity. The physical dimensions of such shop-assembled units are dictated -by the shipping clearances allowed by commercial carriers, so that, once the size of the unit has reached the maximum allowable, any increase in steaming capacity (which requires additional heating surface) must be made at the expense of furnace combustion space. Since flame impingement on the heat exchange surfaces is highly undesirable, the pro-blem of increasing the capacity of -shop-assembled boilers has resolved itself into one of increasing the combustion rate so that less combustion space is required to completely burn a given quantity of fuel, or so that a larger quantity of fuel can be burned within a combustion space of a given size.

Considerable effort has recently been directed toward increasing the capacities of package type boilers. For example, U.S. Patent No. 3,149,614, issued Sept. 22, 1964, in the name of G. Musat et al., discloses a shop-assembled steam generator having a steaming capacity of about 150,000 pounds of steam per hour at a pressure of 435 p.s.i. and a temperature of 750 F. A unit of the type disclosed in the aforementioned patent has been operated satisfactorily at its rated capacity; however, attempts at further increasing its maximum rating have been unsuccessful, the lack of success generally being characterized -by incomplete combustion within the available combustion space when tiring oil, the incomplete combustion not only resulting in the waste of fuel, but also producing a dirty and obnoxious stack discharge characteristic of inefficient operation.

It is therefore the general object of the present invention to provide an improved combustion chamber for a shop-assembled steam generator, whereby the steaming capacity of the steam generator may be increased, by as much -as 30%, above the capacity previously available in units of a comparable physical size. It is a further and more specific object of the invention to provide improvements to the combustion chamber disclosed in U.S. Patent No. 3,149,614, whereby -mixing of the fuel and combustion air is improved to promote rapid ignition and complete combustion, and consequently higher heat release rates within the combustion chamber, so that the capacity of the steam generator may be increased Without a corresponding increase in the volume of the furnace combustion space.

In accordance with the invention, there is provided in a steam generator having a furnace space, fuel burning apparatus comprising end Walls and :a circumferential boundary Wall forming a horizontally -disposed combustion chamber of circular cross section. The circumferential boundary wall of the combustion chamber is formed by oppositely curved rows of spaced steam generating tubes, the intertube spaces being closed by refractory covered metallic studs. A restricted gas outlet, formed in one of the end Walls of the combustion chamber, vopens into the Cil ill)

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furnace space. The combustion chamber is enclosed within a windbox to which superatmospheric combustion air is supplied. Means are provided for introducing cornbustion air from the windbox tangentially into the combustion chamber, which means includes a plurality of circumferentially spaced -air ports, each of which consists of a row of slotted openings formed between the steam generating tubes of the circumferential boundary Wall and eX- tending longitudinally thereof. Each of the air ports has connected around the periphery thereof an air inlet duct, and within each duct immediately upstream air owwise of the lportions of the -steam generating tubes extending across the air port, is disposed means including streamlining elements for preaccelerating the air prior to its passage through the port openings to reduce shock losses across the portions of the tubes extending across the air ports, whereby tangential entry of the air into the cornbustion chamber is promoted. Liquid fuel is introduced into the combustion chamber substantially radially thereof via one or more oil atomizing assemblies extending through the windbox and having their discharge ends terminating substantially flush with the internal surface of the circumferential boundary wall of the combustion chamber circumferentially intermediate an adjacent pair of air ports and longitudinally intermediate the end walls of the combustion chamber.

The various .features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a plan section of a steam generator having fuel burning apparatus constructed in accordance With the invention and .taken along line 1 1 of FIG. 3;

FIG. 2 is a vertical section taken along line 2 2 of FIG. l;

FIG. 3 is a partial vertical section taken along line 3 3 of FIG. 1;

FIG. 4 is a partial sectional view taken along line 4 4 of FIG. 1;

FIG. 5 is a partial sectional view taken along line 5 5 of FIG. 4; and

FIGS. 6A and 6B are diagrammatic vertical cross-sectional views of the cyclone combustio-n chamber depicting oW conditions therein respectively before and after use of air flow streamlining elements in conjunction with the air inlet ports.

In the drawings, FIGS. l, 2 Iand 3, the invention is illustrated as being embodied in a shop-assembled, bottom supported, natural circulation steam generating unit designed to re liquid and/or gaseous fuel. The vapor generating sections of the unit are substantially similar to the unit described in the above-mentioned U.S. Patent 3,149,617 and reference should be made to that patent for a more detailed description. Essentially, the steam generating unit comprises a setting of rectangular c-ross section having upright front and rear walls 10 and 11 respectively, upright opposing side walls 12 and 13, an upper enclosing roof 14 and a lower enclosing oor 15. A pair of parallel upright partition walls 16, extending lengthwise of the setting, divide the setting into an nnobstructed furnace chamber space 17 and a pair of symrnetrically arranged heating gas passes 19 disposed on opposite sides of the furnace space 17. Hot combustion gases supplied to the furnace combustion space 17 from the cyclone type furnace 50 pass along the length of the furnace space 17 -and are divided into a pair of substantially equal streams flowing lengthwise through the heating gas passes 19, in an opposite direction to the flow through the furnace space 17, to the gas outlets 20, from which the gases are either passed over additional heat absorbing surfaces (not shown) or are discharged directly into the atmosphere via 'a stack (not shown). It should be recognized that, as described in U.S. Patent 3,149,614, the walls 10, 11, 12 and 13, the roof 14, the floor 15 and the partition Walls 16 are all provided with heat absorbing tubular members, that the heating gas passes 19 have disposed therein heat absorbing tube banks 22, and that a superheater 23 may be appropriately arranged within the setting. Moreover, it should be recognized that these heat absorbing tubular members Iare appropriately connected for natural circulation through the upper steam and Water drum 24 and the lower drum 25, both of which extend longitudinally of the setting and have their longitudinal axes in a common vertical plane centrally disposed with respect to the setting.

Heating -gases are supplied to the furnace space 17 from a horizontally extending cyclone type furnace 50 disposed adjacent to the front Wall and having its longitudinal or major axis disposed in the same vertical plane las the longitudinal center lines of the furnace space 17 and the drums 24 and 25. While the cyclone furnace construction illustrated and hereinafter described is specifically designed and particularly adapted for firing by oil alone, by natural gas alone or by any combination thereof, it will be understood that the cyclone furnace illustrated may also be adapted for firing by various other kinds of liquid and/or gaseous fuels.

The cyclone furnace Si)` comprises a horizontally elongated combustion chamber 51 of circular cross section, the circumferential boundary wall thereof being formed by oppositely curved rows of wall tubes 52 having their intertube spaces closed, except in the zones of air admission as hereinafter described, by refractory covered metallic studs welded to the tubes. The upper ends of the tubes 52 connect into the overlying portion of the upper drum 24, and their lower ends are connected into the horizontal headers 53 disposed on opposite sides of the longitudinal centerline of yand subjacent combustion chamber 51. The headers 53 Iare connected for fluid supply from the lower drum by tubes (not shown), and from the upper drum 24 by upwardly extending tubes 56 symmetrically arranged on opposite sides of the vertical axis of the drum 24 and extending along the front end of and adjacent to the cyclone furnace 50.

The front or outer end of the combustion chamber 51 is formed by -a circular wall 57 including upwardly extending tubes 58 symmetrically arranged on opposite sides of the vertical axis of the combustion chamber and having their intertube spaces closed by refractory covered metallic studs welded to the tubes 58, with intermediate portions of the tubes 5S being suitably bent to form a centrally disposed circular opening 6G. Tubes 58 have their upper ends connected to the drum 24, the tubes on either side of the vertical axis of the combustion chamber 51 having their lower ends connected to the header 53 on the corresponding side of the combustion chamber axis. The rear or inner end of the combustion chamber 51 is partially closed by a circular wall 61 (which forms a part of the front wall 10) including upwardly extending tubes 62 having their intertube spaces closed by refractory covered metallic studs welded to the tubes 62 and extending -between the drum 24 and the 4headers 53 in substantially the same manner as the tubes 5S, with intermediate portions of the tubes 62 being suitably bent to form a centrally disposed restricted gas outlet 63 through which hot combustion gases pass from the combustion chamber 51 to the furnace space 17.

Air supply provisions for cyclone furnace 5) comprise metallic casing 65 suitably connected to the front wall 10 .and surrounding and spaced from the cyclone furnace 50 to form an enclosing windbox 66 to which superatmospheric combustion air is supplied by `a pair of ducts 67 opening to the top Vof the windbox 66 and connected to a forced draft fan (not shown). Casing 65 may be formed with an aperture 68, closed by a circular cover plate 69 in which may be mounted a sighting tube or flame detector 70. A vertical partition wall 71, disposed adjacent the front end of the cyclone furnace 50, cooperates with a horizontally disposed divider plate 72, extending between the partition wall 71 and the front wall of the windbox casing 65, to form a separate windbox chamber 66A at the front end of the windbox 66. The flow of air to the charnber 65A from the windbox 66 is suitably controlled by means of -a blade damper 68 disposed in the divider plate 72.

A relatively minor portion of the combustion air flows into the combustion chamber 51 from the chamber 66A through a frusto-conical air register 74 which is connected to the front circular wall 57 around the periphery of the opening 69 and extends into the chamber 66A to a position closely adjacent the front wall of the windbox casing 65. The remaining major portion of combustion air enters the cyclone combustion chamber 51 directly from the windbox via the four air inlet assemblies 75 circumferentially spaced around the circumferential boundary Wall of the combustion chamber 50. It will be recognized that the apportionment of combustion air between the air register 74 and the air inlet assemblies 75 may be effected, within limits, by manipulation of the damper 68.

Each of the air inlet assemblies 75 includes a duct 76 of substantially rect-angular cross section extending along substantially the entire length of the combustion chamber 51, and having its inlet end open to the windbox 66 and its discharge end lopening tangentially into the combustion chamber 51 by way of an air port 77 extending substantially the entire length of and formed in the circumferential boundary w-all of the combustion chamber 51. Each air port 77 comprises a plurality of spaced, circumferentially extending slotted openings 77A formed between the Wall tubes 52, the width of each opening 77A being preferably approximately equal to the diameter of the wall tubes 52. To promote the tangential entry of the air into the combustion chamber 51, there is provided Within each duct 76, immediately upstream of each of the portions of the Wall tubes 52 extending across an air port 77, a streamlining element comprising a pair of plates 80A, the forward (downstream air flowwise) ends of which are suitably connected to the sides of a wall tube 52, and the rearward (upstream air owwise) ends of which are joined togther so as to present a substantially sharp edge 80B to the stream of air flowing through the duct 76. The edges 80B of the streamlining elements 3l) extend the entire height of the duct and are disposed substantially normal to the direction of air dow therethrough. VEach `of the streamlining elements 80 preferably has a length at least equal to the height of the air inlet duct 76 in which it is disposed.

In iiow model studies conducted in the laboratory facilities of the assignee of the present invention, it was found that without the streamlining elements Si), the air approach Velocity to the portions of the Wall tubes 52 extending across the air ports 77 was low, and there was a substantial shock loss across the tubes 52, which phenomena resulted ina low penetrating power of the air streams discharged into the combustion chamber 51; moreover, since the portions of the tubes 52 are angularly disposed with respect to the direction of flow of the incoming air stream there was a tendency for the air to be deflected from its original direction so that it discharged into the combustion chamber at an angle approaching a right angle with respect to the tangent line of the wall tubes 52 at the location of the air port 77. The net result was, as shown in FIG. 6A, a substantial radial (nontangential) component of velocity leaving the air ports 57, thus resulting in low tangential inlet air velocities and the formation of eddy currents along the circumferential boundary wall of the combustion chamber 51. In actual operation, when firing oil such eddy currents were found to fasten the formation of deleterious coke deposits on the inside wall of the combustion chamber.

Additional flow model studies indicated that by using the flow streamlining elements 80, the air approach velocities to the wall tubes 52 could be increased, the shock losses `could be eliminated by means of the sharpapproach edges 80B, and the tendency of the air flow stream to be discharged normally to the tangent of the wall tubes 52 could be eliminated. Thus, the net result of the use of the flow .streamlining elements 80 (as shown in FIG. 6B) is an increase in tangential air velocity entering the combustion chamber 5l, the substantial elimination of the undesirable radial air velocity components and eddy currents, and consequently improved cyclonic action. The laboratory model studies were substantiated in the field where the use of ow streamlining elements 80 produced improved fuel and air mixing in the combustion chamber 51 with consequent higher heat release rates therein.

Gaseous fuel may be introduced tangentially into the combustion chamber 51 through a plurality of tubular gas burners 85 disposed at spaced locations along the lengths of the air ducts 76 and terminating ywithin the openings 77A of the air ports 77. As shown in FIG. 4, perforated plates 88 may be placed over those of the openings 77A through which the gas burners 85 extend, the effect of the perforated plates 88 being to reduce the air velocity in the vicinity of the discharge ends of the gas burners 85 and to improve air distribution for purposes of stabilizing ignition of the gaseous fuel. Gaseous fuel is supplied to the burners 85 Within each duct 76 by a branch manifold 86, with each pair of manifolds 86 on each side of the vertical axis of the combustion chamber 51 being connected to a common gas supply manifold 87 extending through the windbox casing 65 and connected to a supply of gaseous fuel (not shown).

Fuel oil is introduced into the combustion chamber 51 through oil atomizer assemblies 90 connected to a suitable source of fuel oil (not shown) and arranged to direct (preferably hollow) conical sprays of finely atomized oil droplets substantially radially into the combustion chamber 51. Although it is preferred that the atomizer assemblies 90 be of the type wherein atomization is assisted by an expansible fluid (such as steam or air), it should be understood that any type of oil atomizing assembly is contemplated as being within the purview of the present invention. Each of the atomizer assemblies 99 extends through the windbox 66 in a direction substantially perpendicular to the axis of the combustion chamber 5l. The discharge ends 90A of the atomizer assemblies 90 terminate substantially flush with the internal surface of the circumferential boundary wall of the combustion chamber 51, circumferentially intermediate adjacent air ports 77 and longitudinally intermediate the end walls 57 and 63. The inlet ends of the atomizer assemblies 90, on which are mounted suitable couplings 90B for connection to the oil and atomizing fluid supply lines, extend outside the windbox casing 65 Where they a-re readily accessible for purposes of removal and ycleaning of the atomizer assemblies 90. The atomizer assemblies 90 may be mounted directly opposite each other as sho-wn in FIG. 1, or they may be staggered along the length of the combustion chamber 51.

By introducing the oil radially into the combustion cham-ber 51 as described above, the maximum average distance of travel of the oil droplets from the atomizer discharge end 90A Vto the projected point of impingement on the combustion chamber boundary -w-all is afforded, thus providing maximum opportunity for ignition of all the oil droplets. Immediately upon discharge of the oil spray from the atomizer assembly 90, the spray of oil droplets is swept Iby the high velocity air stream rotating about the inner surface of the circumferential boundary wall. This high velocity air stream ignites the smaller oil droplets and carries them along with the air stream. The larger heavier oil droplets penetrate the high velocity air stream and, during the period of travel Vacross the relatively quiescent center of the combustion chamber 51, are volatilized `and ignited. The centrifugal force within the combustion chamber 51 eventually carries these heavier droplets into the outer swirling air stream wherein the major portion of the combustion is completed ibefore the hot gases are discharged through the gas outlet 63 into the furnace space 17. It should be recognized that the radial oi-l introduction, in combination with the high velocity swirling air stre-am within the combustion chamber, virtually precludes the impingement of raw oil droplets from the combustion chamber wall, and therefore substantially eliminates any possibility of the formation of deleterious coke deposits within the cyclone furnace 50'. Moreover, it has been found that t'he radial introduction of oil, in combination with the improved cyclonic action due to the use of streamlining elements 4Si) results in higher heat release rates within the combustion chamber S1 and consequently `less combustion within the limited volume of furnace space 17.

While in accordance with the provisions of the statutes there is illustrated and described herein a specific embodiment of the invention, those skilled in the art will understand that changes may be made in the form of the invention covered by the claims, :and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.

What is claimed is:

1. In a steam generator having a furnace space, fuel burning apparatus comprising end Iwalls 'and a circumferential -boundary wall forming a horizontally disposed combustion chamber of circular cross-section, walls deiining a windbox enclosing said combustion chamber, means for supplying combustion air to said windbox, the circumferential boundary wall of said combustion chamber being formed by oppositely curved rows of spaced steam generating tubes, the intertube spaces being closed by refractory material, means forming a restricted gas outlet in one of said end walls opening from said combustion chamber to said furnace space, means for intro ducing com-bustion air from said windbox tangentially into said combustion chamber comprising means forming a plurality of circumferentially spaced air ports extending longitudinally of said circumferential boundary wall, said air ports comprising rows of slotted openings formed between the steam generating tubes of said circumferential boundary wall, an air inlet duct associated with each of said air ports, the discharge ends of said air inlet ducts being connected to said circumferential boundary wall around the peripheries of said air ports, and means disposed within said air inlet ducts immediately upstream air owwise of the portions of said steam generating tubes extending across said air ports for preaccelerating the air prior to passing through said openings to reduce shock losses across said portions of said steam generating tubes lwhereby tangential entry of the air into said combustion chamber is promoted, and mean-s for introducing liquid fuel into said combustion chamber.

2. In a shop-assembled steam generator lhaving a furnace space, fuel burning apparatus comprising end walls `and a circumferential boundary wall forming a horizontally disposed combustion chamber of circular cross-section, walls defining a windbox enclosing said combustion chamber, means for supplying combustion air to said windbox, the circumferential boundary Wall of said combustion chamber being formed by oppositely curved rows of spaced steam generating tubes, the intertube spaces being closed 'by refractory material, means forming a restricted gas outlet in one of said end walls opening from said combustion chamber to said furnace space, means for introducing combustion air from said windbox tangentially into said combustion chamber comprising means forming a plurality of circumferentially spaced air ports extending longitudinally of said circumferential boundary wall, said air ports comprising rows of slotted openings formed between the steam -generating tubes of said circumferential boundary Wall, an air inlet duct associated with each of said air ports, the discharge ends of said air inlet ducts being connected to said circumferential boundary wall around the peripheries of said air ports, and means disposed Vwithin said air inlet ducts immediately upstream air flow-Wise of the portions of said steam generating tubes extending across said air ports for pre-accelerating the air prior to passing through said openings to reduce shock losses across said portions of said steam generating tube where-by tangential entry of the air into said combustion chamber is promoted, said last named means comprising streamlining elements connected to the upstream sides of said portions of said Isteam generating tubes and extending upstream thereof and terminating in a substantially sharp edge, and means for introducing liquid fuel into said combustion chamber substantially radially thereof.

3. In a shop-assembled steam generator having a furnace space, fuel burning apparatus comprising end walls and a circumferential boundary wall forming a horizontally disposed combustion chamber of circular cross-section, walls defining a windbox enclosing said combustion chamber, means for supplying combustion air to said windbox, the circumferential boundary wall of said combustion chamber being formed by oppositely curved rows of spaced steam generating tubes, the intertube spaces being closed by refractory material, means forming a restricted gas outlet in one of said end walls opening from said combustion chamber to said furnace space, means for introducing combustion air from said windbox tangentially into said combustion chamber comprising means forming a plurality of circumferentially spaced air ports extending longitudinally of said circumferential boundary wall, said air ports comprising rows of slotted openings formed between the steam generating tubes of said circumferential boundary wall, an air inlet duct associated with each of said air ports, the discharge ends of said air inlet ducts being connected to said circumferential boundary wall around the peripheries of said air ports, and means disposed within said air inlet ducts immediately upstream air owwise of the portions of said steam generating tubes extending across said air ports for preaccelerating the air prior to passing through said openings to reduce shock losses across said portions of said steam generating tubes whereby tangential entry of the air into said combustion chamber is promoted, said last named means comprising streamlining elements connected to the upstream sides of said portions of'said steam generating tubes and extending upstream thereof and terminating in a substantially sharp edge, the edges of said elements eX- tending the entire height of said air inlet ducts and being disposed substantially normal `to the direction of air flow through said air inlet ducts, said elements having a length at least equal to the height of said air inlet ducts, and means for introducing liquid fuel into said combustion chamber substantially radially thereof.

4. In a shop-assembled steam generator having a furnace space, fuel burning apparatus comprising end walls and a circumferential boundary Wall forming a horizontally disposed combustion chamber of circular cross-section, walls defining a windbox enclosing said combustion chamber, means for supplying combustion air to said windbox, the circumferential boundary wall of said combustion chamber being formed by oppositely curved rows of spaced steam generating tubes, the intertube spaces being closed by refractory material, means forming a restricted gas outlet in one of said end walls opening from said combustion chamber to said furnace space, means for introducing combustion air from said windbox tangentially into said combustion chamber comprising means forming a plurality of circumferentally spaced air ports extending longitudinally of said circumferential boundary wall, said air ports comprising rows of slotted openings formed between the steam generating tubes of said circumferential boundary wall, and an air inlet duct associated with each of said air ports, the discharge ends of said air inlet ducts being connected to said circumferential boundary wall around the peripheries of said air ports, and means disposed within said air inlet ducts irnmediately upstream air owwise of the portions of said steam generating tubes extending across said air ports for preaccelera-ting the air prior to passing through said openings to reduce shock losses across said portions of said steam generating tubes whereby tangential entry of the air into said combustion chamber is promoted, and means for introducing liquid fuel into said combustion chamber substantially radially thereof comprising an oil atomizing assembly extending through said windbox in a direction perpendicular to the axis of said combustion chamber and having its discharge end terminating substantially ush with the internal surface of the circumferential boundary Wall of said combustion chamber between adjacent air ports.

5. In a shop-assembled steam generator having a furnace space, fuel burning apparatus comprising end walls and a circumferential boundary wall forming a horizontally disposed combustion chamber of circular cross-section, walls defining a windbox enclosing said combustion chamber, means for supplying combustion air to said windbox, the circumferential boundary wall of said cornbustion chamber being formed by oppositely curved rows of spaced steam generating tubes, the intertube spaces being closed by refractory material, means forming a restricted gas outlet in one of said end walls opening from said combustion chamber to said furnace space, means for introducing combustion air from said windbox tangentially into said combustion chamber comprising means forming a plurality of circumferentially spaced air ports extending longitudinally of said circumferential boundary wall, said air ports comprising rows of slotted openings formed between the steam generating tubes of said circumferential boundary wall, and an air inlet duct associated with each of said air ports, the discharge ends of said air inlet duc-ts being connected to said circumferential boundary wall around the peripheries of said air ports, and means disposed Within said air inlet ducts immediately upstream air ilowwise of the portions of said steam generating tubes extending across said air ports for preaccelerating the air prior to passing through said openings to reduce shock losses across said portions of said steam generating tubes whereby tangential entry of the air into said combustion chamber is promoted, said last named means comprising streamlining elements connected to the upstream sides of said portions of said steam generating tubes and extending upstream thereof and terminating in a substantially sharp edge, and means for introducing liquid fuel into said combustion chamber substantially radially thereof comprising a pair of oil atomizing assemblies disposed on opposite sides of and extending through said windbox in opposite directions perpendicular to the axis of said combustion chamber and having their discharge ends terminating substantially Hush with the internal surface of the circumferential boundary Wall Aof said combustion chamber on opposite sides thereof at locations circumferentially intermediate said air ports and longitudinally intermediate the end Walls of said cornbustion chamber.

6. In a shop-assembled steam generator having a furnace space, fuel burning apparatus comprising end walls and a circumferential boundary wall forming a horizontally disposed cylindrical combustion chamber'of `circular cross-section, walls defining a windbox enclosing said combustion chamber, means for supplying COmbUSlOn air to said windbox, the circumferential boundary yvall of said combustion chamber being formed by 0Pp0 S1e1y curved rows of spaced steam generating tubes, the intertube spaces being closed by refractory material, means forming a restricted gas outlet in one of said end walls opening from said combustion chamber to said furnace space, means for introducing combustion air from said windbox tangentially into said combustion chamber comprising means forming a plurality of circumferentially spaced air ports extending longitudinally of said circumferential boundary wall along substantially the entire length thereof, said air ports comprising rows of slotted openings formed between the steam generating tubes of said circumferential boundary Wall, and an air inlet duct associated with each of said air ports, the discharge ends of said air inlet ducts being connected to said circumferential boundary wall around the peripheries of said air ports, and means disposed within said air inlet ducts immediateiy upstream air flowwise of the portions of said steam generating tubes extending across said air ports for preaccelerating the air prior to passing through said openings to reduce shock losses across said portions of said steam generating tubes whereby tangential entry of the air into said combustion chamber is promoted, said last named means comprising streamlining elements connected to the upstream sides of said portions of said steam generating tubes and extending upstream thereof and terminating in a substantially sharp edge, the edges of said elements extending the entire height of said air inlet ducts and being disposed substantially normal to the direction of air flow through said air inlet ducts, said elements having a length at least equal to the height of said air inlet ducts, and means for introducing conical sprays of liquid fuel into said combustion chamber substantially radially thereof comprising a pair of oil atomizing assemblies disposed on opposite sides of and extending horizontally through said 'windbox in opposite directions perpendicular to the axis of said combustion chamber and having their discharge ends terminating substantially flush with the internal surface of the circumferential boundary wall of said combustion chamber on opposite sides thereof at locations circumferentially intermediate said air ports and longitudinally in the central portion of said combustion chamber.

7. In a steam generator having a furnace space, fuel burning apparatus comprising walls including steam generating tubes forming a substantially horizontal combustion chamber of circular cross-section having a restricted gas outlet at one end opening to said furnace space, fuel supply means for discharging liquid fuel radially into the combustion chamber, and air supply means for introducing into the chamber all the air required for combustion at locations separate from the point of entry of the fuel and in a manner producing whirling streams of air having the same direction of rotation and coursing through chamber in a helical ow path, said air supply means including means for introducing combustion air tangentially into the combustion chamber and effecting a helical path of travel therein along the circumferential wall of said chamber, said fuel supply means including a liquid fuel atomizing assembly having a discharge end terminating substantially flush with and contiguous to the internal surface of the circumferential wall of the combustion chamber and arranged to introduce liquid fuel radially into the combustion chamber so as to intimately mix and whirl with the combustion air after the air enters the chamber.

8. In a steam generator having a furnace space, fuel burning apparatus comprising Walls including steam generating tubes forming a substantially horizontal combustion chamber of circular cross-section having a restricted gas outlet at one end opening to said furnace space, fuel supply means for discharging liquid fuel radially into the combustion chamber, and air supply means for introducing into the chamber all the air required for combustion at locations separate from the point of entry of the fuel and in a manner producing whirling streams of air having the same direction of rotation and coursing through the chamber in a helical flow path, said air supply means including means for introducing combustion air tangentially into the combustion chamber and effecting a helical path of travel therein along the circumferential wall of said chamber, said fuel supply means including a pair of liquid fuel atomizing assemblies .disposed on diametrically opposite sides of the chamber, each assembly having a discharge end terminating substantially ush with and contiguous t0 the internal surface of the circumferential wall of the combustion chamber and arranged to introduce liquid fuel radially into the combustion chamber so as to intimately lmix and whirl with the combustion air after the air enters the chamber.

References Cited UNITED STATES PATENTS 3,115,122 12/1963 Stallkamp 122--235 3,149,614 9/1964 Musat et al. 122--235 3,186,382 6/1965 Wieser 110-28 X CHARLES J. MYHRE, Primlary Examiner. 

1. IN A STEAM GENERATOR HAVING A FURNACE SPACE, FUEL BURNING APPARATUS COMPRISING END WALLS AND A CIRCUMFERENTIAL BOUNDARY WALL FORMING A HORIZONTALLY DISPOSED COMBUSTION CHAMBER OF CIRCULAR CROSS-SECTION, WALLS DEFINING A WINDBOX ENCLOSING SAID COMBUSTION CHAMBER, MEANS FOR SUPPLYING COMBUSTION AIR TO SAID WINDBOX, THE CIRCUMFERENTIAL BOUNDARY WALL OF SAID COMBUSTION CHAMBER BEING FORMED BY OPPOSITELY CURVED ROWS OF SPACED STEAM GENERATING TUBES, THE INTERTUBE SPACES BEING CLOSED BY REFRACTORY MATERIAL, MEANS FORMING A RESTRICTED GAS OUTLET IN ONE OF SAID END WALLS OPENING FROM SAID COMBUSTION CHAMBER TO SAID FURNACE SPACE, MEANS FOR INTRODUCING COMBUSTION AIR FROM SAID WINDBOX TANGENTIALLY INTO SAID COMBUSTION CHAMBER COMPRISING MEANS FORMING A PLURALITY OF CIRCUMFERENTIALLY SPACED AIR PORTS EXTENDING LONGITUDINALLY OF SAID CIRCUMFERENTIAL BOUNDARY WALL, SAID AIR PORTS COMPRISING ROWS OF SLOTTED OPENINGS FORMED BETWEEN THE STEAM GENERATING TUBES OF SAID CIRCUMFERENTIAL BOUNDARY WALL, AN AIR INLET DUCT ASSOCIATED WITH EACH OF SAID AIR PORTS, THE DISCHARGE ENDS OF SAID AIR INLET DUCTS BEING CONNECTED TO SAID CIRCUMFERENTIAL BOUNDARY WALL AROUND THE PERIPHERIES OF SAID AIR PORTS, AND MEANS DISPOSED WITHIN SAID AIR INLET DUCTS IMMEDIATELY UPSTREAM AIR FLOWWISE OF THE THE PORTIONS OF SAID STEAM GENERATING TUBES EXTENDING ACROSS SAID AIR PORTS FOR PREACCELERATING THE AIR PRIOR TO PASSING THROUGH SAID OPENINGS TO REDUCE SHOCK LOSSES ACROSS SAID PORTIONS OF SAID STEAM GENERATING TUBES WHEREBY TANGENTIAL ENTRY OF THE AIR INTO SAID COMBUSTION CHAMBER IS PROMOTED, AND MEANS FOR INTRODUCING LIQUID FUEL INTO SAID COMBUSTION CHAMBER. 